Forty years ago, Caterpillar rolled out 10 pilot models of the D10, the world’s largest and most powerful bulldozer and the time, and one equipped with an elevated sprocket design that would change the face of the dozer market.
“We bucked conventional wisdom with the D10 and tinkered with a centrepiece that was a part of the Caterpillar product line since the company was formed in 1925,” says George Alexander, a retired Caterpillar engineer and one of four individuals named on the patent for the elevated sprocket.
Weighing in at 86 tonnes, and measuring 4.6m tall, 3.7m wide and 9.4m long, the result was a unit with unrivalled power and productivity, and one that answered the growing calls from large mining and big heavy construction operations for a more powerful dozer.
The Cat D10’s power was supplied by a 522kW (700hp) D348, V12 diesel engine, and delivered 50% greater productivity than Caterpillar’s previous largest dozer, the Cat D9.
The impetus for the development of the D10 was a changing industry in the late 1960s and early 1970s that stretched the productivity limits of the D9, and led contractors working in hard rock applications to demand a design that improved track longevity and durability.
“The D9 dozer was the best track-type tractor of the day,” explains Alexander. “It worked great for dirt operations, but interstate and heavy rock applications were hard on the solid bottom tracks that were a part of all dozer designs of that era.”
So, Caterpillar tasked a team of research and engineering personnel to develop a model with more power and productivity, as well as a modular design that would simplify the maintenance and transport of the machine.
Through the research process, it quickly became evident that a new track design and improved undercarriage were needed to meet the production and durability goals for the new dozer.
With management approval in 1970, a test bed was built for the new track, and engineers started by flipping the final drive for a D9G upside down. “We worked on undercarriage geometry a lot, and within six months we had it operational,” says Alexander.
By separating the drive sprockets from the track roller frame and elevating them above the tracks, more track remained on the ground for improved traction. The elevated sprocket design was also better able to absorb ground shocks for longer life and greater operator comfort.
Two years of thorough testing in multiple demanding applications led to the first elevated sprocket patent application and building the first two D10 prototypes in August 1973.
In all, the Caterpillar team working on the project generated 93 patents with the new concept.
While initial testing proved the efficacy of the elevated sprocket design, there were still some sceptics of the new design.
“It didn’t look like any previous Cat dozer,” notes Alexander. “The machine was different in almost every way, except for the engine.”
However, the pilot D10 dozers built in 1977 were quicklymbraced by Caterpillar customers.
Their ripping and pushing capabilities then proceeded to have a significant impact in the mining industry, after studies showed the cost/yard to move material using the D10 was comparable to that of much larger draglines.
The resilient undercarriage with elevated sprocket meanwhile conformed to the ground better than solid tracks, helping to improve machine pushing power and undercarriage life.
The dozer’s modular concept helped to increase machine transportability, as removable components facilitated machine moves from location to location. Its modular design also substantially advanced assembly and service task efficiency.
The transmission and bevel gear removal and installation times dropped from 30 hours on the D9H to just six hours on the D10, while the service time plummeted from 45 hours to just nine hours, lowering the operating costs.
Today, the legacy of the D10 lives on in thousands of Caterpillar elevated sprocket dozers operating around the world.
The basic concept has now been expanded to today’s Cat D6 medium dozers, the D8T, D9T and D11T large dozers, and the current D10T2 model.
“After I retired in the 1990s, I gave a presentation on the development of the elevated sprocket design, and afterwards an attendee said to me: ‘Wherever you go, you will see the results of your work’,” recalls Alexander.
“He was right. No matter where I travelled, I saw dozers with the elevated sprocket design, and it made me proud to be a part of the original research team.”
